Progress of advanced information society in recent years has caused increasing power consumption of electronic apparatuses, such as computers, which are served as information processing apparatuses. Therefore, the electronic apparatuses have been designed to include a plurality of power supply devices by which electric power can be supplied. For example, there is a known technology for a power supply system in which four power supply devices with a power capacity of 1,500 W are mounted on an electronic apparatus with a power consumption of 6,000 W.
In addition, another technology, which has been known in the art, is to change the number of power supply devices to be operated depending on load variation.
Japanese Laid-open Patent Publication No. 9-56064, Japanese Laid-open Patent Publication No. 2009-201244, Japanese Laid-open Patent Publication No. 10-201090, Japanese Laid-open Patent Publication No. 2003-348819 are examples of related art.
A power supply device (hereinafter, also referred to as a power supply unit), which has been used in the conventional electronic apparatus, is designed to adapt to both the operating state and the stand-by state of the electronic apparatus. That is, the power supply unit is constructed of a high-efficiency main power supply and a built-in stand-by power supply with efficiency lower than that of the main power supply. The power supply unit has two or more outputs, one from the main power supply and the other from the stand-by power supply. The electronic apparatus is provided with a service processor for system management. The service processor checks the hardware configuration of the apparatus including a central processing unit (CPU), a memory, a power supply unit, a cooling fan, and so on in the electronic apparatus in the stand-by state. Then, the service processor performs the start-up of the power supply unit and the fan when the electronic apparatus changes from the stand-by state to the operating state. Also, the service processor performs the shut off of the power supply unit and the fan when the electronic apparatus changes from the operating state to the stand-by state.
In the power supply unit with a plurality of outputs, including the main power supply and the stand-by power supply, the main power supply has been designed to have high efficiency to prevent the main power supply from generating internal heat due to a large output current from the main power supply. On the other hand, the stand-by power supply has been designed to have small efficiency when compared with the main power supply because of a small output current from the stand-by power supply.
However, in recent years, the trends to lower power consumption of the electronic apparatus is to enhance the efficiency of power supply in the state ranging from the low-load idle state where the operating load factor of the electronic apparatus is low to the high-load state where the operating load factor of the electronic apparatus is high. Therefore, the presence of the stand-by power supply, which has low efficiency compared with the main power supply, has been a barrier that prevents the power supply unit from becoming high efficiency.
Since the power supply unit with a plurality of outputs having the stand-by power supply includes two or more power supply circuits, the overall power supply circuit of the power supply unit is complicated. Thus, there is a problem in that a volume per power of the power supply unit is larger than that of a power supply unit only having the output of a main power supply. Furthermore, a power supply unit provided with both the main power supply and the stand-by power supply results in additional manufacturing cost for the circuit of the stand-by power supply.
The power loss of the power supply unit can be roughly classified into the following two types: one is power loss due to the flow of current, i.e., a conduction loss represented by I×I×R; and the other is power loss due to the presence of a power-supply control circuit, a switching drive circuit, and so on irrespective of current, i.e., driving loss Pd.
The conduction loss I×I×R increases in proportion to the square of current. Thus, the power supply unit depicts high efficiency at a load factor of approximately 75% of rated power. For example, the power supply unit becomes 90% of efficiency at a load factor of 80%.
In general, the power supply unit is preferably used with an appropriate load factor for assuring high efficiency of power supply efficiency. It is common to mount a plurality of power supply units on the electronic apparatus that requires the power supply ability of “n” power supply units in practical operation. Specifically, for example, it can be attained by way of “n+1” redundant configuration in which an additional power supply unit is placed, a duplicated power receiving system configuration in which the power supply line is doubled, or several additional power supply units which are mounted in consideration of future enhancement. Therefore, the electronic apparatus having a plurality of power supply units, for example four units, has a small load factor per unit. Thus, each of these power supply units is used with a low load factor. As a result, there is a program in that power supply efficiency decreases each of these power supply units is used with a low load factor. For example, each power supply unit may be used with a load factor of 20% and then each power supply unit may result in an efficiency of 25%. Furthermore, depending on the operation state of the electronic apparatus, a decrease in power supply efficiency may occur even in the case of a decrease in load factor.
For electronic apparatuses of recent years, the types and the numbers of memories, CPUs, and different units to be mounted have been increased. In addition, such electronic apparatuses may use large scale integrated circuits (LSI) that require setting of initial operating conditions. In the stand-by state before the electronic apparatus will shift to the operating state, a stand-by current tends to be increased because the service process for setting the initial operating conditions and checking errors operate in the stand-by state.
However, there is a disadvantage in that a high-current stand-by power supply with low efficiency leads to an increase in heat generation. In addition, there is another disadvantage in that mounting a high-current stand-by power supply with high efficiency requires a complicated control circuit and leads to increases in size and cost of the power supply unit.
Furthermore, there is a problem in that the power supply unit with a low stand-by voltage, such as the power supply unit with a 3.3V (volt) power supply unit or a 5V power supply unit, is difficult to prevent system down when a voltage reduction occurs. That is, the original voltage is as low as 3.3V. In some cases, therefore, the 3.3V-operating electronic apparatus may hardly continue its operation because of short circuit in any of other circuit boards. In the case of the configuration of the electronic apparatus in which a fuse-resistance-diode-capacitor circuit is placed on the input side of a resident power supply line that supplies electric power to a board, the output voltage of the power supply may decrease from 3.5V to a minimum of 2.5V.
In addition, when connecting an alternating current (AC) cable to each power supply unit, a voltage reduction may occur due to over-current if the stand-by current required for the units of the electronic apparatus is large and exceeds the ability of an AC power supply device to supply electric power to each of the power supply unit.
Therefore, the configuration of the electronic apparatus in which a plurality of power supply units having two or more outputs is installed has several disadvantages, such as a reduction in efficiency.
The technology disclosed herein have been made in consideration of the above description and intends to provide a power supply system, an electronic apparatus, and a method for controlling such a power supply system in which the efficiency of power supply is improved.
In the power supply system, the electronic apparatus, and the method for controlling the power supply system disclosed in the present application, a plurality of power supply units where their output terminals are connected to one another in parallel inputs first voltage to a plurality of load units. Then a management control unit outputs a stand-by signal based on configuration information representing the configuration of each load unit to any of the power supply units. The plurality of power supply units shut off the output of the first output voltage in response to the stand-by signal.
In addition, the power supply system, the electronic apparatus, and the method for controlling the power supply system disclosed in the present application outputs first output voltage from a power supply section of a power supply unit in the power supply system to the load unit. A voltage-dividing part of the load unit receives the first output voltage as an input, outputs a second output voltage to an operation part of the load unit in response to instructions from the management control unit, and outputs a third output voltage as long as an input voltage is input.
The power supply system, the electronic apparatus, and the method for controlling the power supply system disclosed in the present application exert advantageous effects of providing those with improved power supply efficiency.